A self-luminous organic EL display employing an organic light emitter such as diamines has been the focus of attention in recent years as a next-generation flat panel display in place of a liquid crystal display (LCD) and a plasma display panel (PDP). As shown in FIG. 1 for example, this organic EL display has a structure that an EL element substrate 1 made of glass has one of the surfaces (an inner surface) formed with, sequentially from the bottom, a lower electrode 2 in a parallel striped pattern, an organic light-emitting layer 3, and an upper electrode 4 in a parallel striped pattern extending along an orthogonal direction to the lower electrode 2, and that between peripheral portions of the EL element substrate 1 and a sealing glass plate 5 arranged opposed thereto are sealed by a sealing layer 6.
This kind of organic EL display has many advantages; the display has high luminance, high contrast, and excellent display recognizability, can be formed extremely thin in thickness, is applicable also to an ultra-thin display having a total thickness of 1 mm or thinner for use in small devices such as a cell-phone (a cellular mobile telephone) and a digital camera, can be constructed of solid materials in its entirety, and is driven with direct current, so that a driving circuit thereof is simplified. On the other hand, there is a drawback that luminescence characteristics of the organic EL element are significantly deteriorated by contact with moisture. Therefore, the establishment of a sealing technique for cutting off the organic EL element from the outside air has been a major challenge.
At present, a sealing method with use of glass frits and a laser is considered to be the leading candidate as a sealing means for the organic EL display. That is, the glass frits form a sealing glass layer in such a manner that a powder mixture whose components are mainly metal oxides is heated, melted, vitrified, and then pulverized into a powder and the power is brought into paste form by a solution in which an organic binder is usually dissolved in an organic solvent, and the paste is coated on a sealed portion and melted again by heating. Recently, glass frits of a variety of glass compositions free from toxic lead are in practical use and frequently used for sealed portions for keeping an interior of LCDs, PDPs, and vacuum fluorescent displays (VFDs) under high vacuum. Therefore, the glass frits are considered suitable also for cutting off a moisture-sensitive organic EL element from the outside air. However, a sealing temperature of general glass frits is 400° C. or more, so that the organic EL display may have a problem in sealing by in-furnace heating that an organic EL element is damaged or thermally degraded under the influence of high temperature. Thus, promising in sealing of the organic EL display is a method that a laser beam is irradiated on panel peripheral portions between which the glass frits intervene, and only the glass frits are locally heated and melted, and then thermal adverse effects on the organic EL element are suppressed (Patent Documents 1 to 4). It is noted that such laser sealing also has the advantage that a sealing time can be reduced greatly as compared with the sealing by in-furnace heating.